This invention relates to heat treatment of grain, and more particularly, for the purpose of controlling moisture content of grain and insect infestation.
When moisture content of stored agricultural products (e.g., grain and cereals) exceeds acceptable limits, the products can deteriorate rapidly, leading to the development of mold and potentially dangerous toxins. In addition, storage of agricultural products (e.g., in silos) having high moisture can significantly increase the likelihood of insect infestation. These problems are particularly problematic in wet and/or high humidity climates.
To control moisture content, heaters and blowers can be used to dry the product before delivery. Drying in wet areas and conditions in this manner has become a routine procedure on farms, and can be costly and time-consuming. In addition to drying, agricultural product stored in bulk silos is normally treated with chemicals such as phosphine to prevent fungi and insects from proliferating and destroying the product. Although the chemicals have been helpful in saving the product from insect destruction, they are not always completely effective and pose a great danger to personnel handling them. Additionally, since the chemicals are not desirable for human consumption, the chemical residues on the treated product must be held below certain levels for safe consumption as human food.
The invention relates to a system which provides selective and volumetric heating of material within a containment vessel in a safe manner. This approach is used to advantageously remove moisture stored with agricultural products (e.g., grain), and in certain applications, increase the mortality of insects living within the agricultural product stored in the containment vessel.
In one general aspect of the invention, the heating system includes a transmission network configured to receive electromagnetic energy and having a first conductor extending substantially along a longitudinal axis of the containment vessel, and at least one additional conductor disposed parallel to the first conductor and positioned near a surface of a wall of the containment vessel.
Various implementations of this aspect of the invention may include one or more of the following features.
The first conductor is positioned to effectively radiate the contents of the containment vessel. For example, in one implementation, the first conductor is disposed substantially along a longitudinal axis of the containment vessel. The additional conductor is disposed substantially in parallel to the first conductor, for example, within the containment vessel.
In other embodiments, there may be a number of additional conductors spaced from the first conductor. For example, the wall of the containment vessel may be cylindrically-shaped with the additional conductors spaced around, or even embedded within, the perimeter of the wall.
The system includes an air blower connected to the grain containment vessel, and a heat exchange system connected to the grain containment vessel. The system can include an electromagnetic energy source connected to the first conductor.
In certain embodiments, one or more of the conductors are positioned outside the containment vessel and provide electromagnetic energy through an aperture contained in the containment vessel wall. In this embodiment, a grain vapor extraction system may be used to provided additional heating within the containment vessel.
In another aspect, the invention features a method for removing moisture from grain in a containment vessel, including positioning an antenna in the containment vessel and operating the system to radiate energy to heat moisture in the grain.
Embodiments of this aspect of the invention may include one or more of the following features.
The method includes operating the system to radiate sufficient energy to remove moisture from the grain. Airflow is provided into the grain to move heated air within the containment vessel to provide uniform heating of the grain. The airflow is continuously provided through the grain to keep the heat of the grain below the latent heat of vaporization of water. The method further comprises increasing the mortality of insects within the grain by operating the antenna to radiate energy to heat the insects in the grain. For example, the electromagnetic energy is provided at a frequency (e.g., 1 MHz to 1000 MHz), power level (e.g., 10 Kwatts to 50 Kwatts) and duration (e.g., 3 to 13 seconds) which is lethal to insects.
Among other advantages, the heating system and method described above, controls grain moisture levels and increases the mortality of insects present in grain containment vessels. The system and method accomplishes these advantages through selective energy absorption, while operating the systems at low energy levels, thereby realizing a significant energy saving: Further advantages include providing insect and fungus control without the use of toxic chemicals.
In yet another aspect, the invention features a method of measuring the moisture content of grain in a containment vessel, including placing an electromagnetic device in the containment vessel, operating the electromagnetic device to radiate a first energy into the grain, measuring a second energy emanating from the grain, comparing the second energy emanating from the grain to the first energy radiating into the grain, extracting a first electromagnetic parameter from the comparison of the first and second energies, comparing first electromagnetic parameter with a known dry grain electromagnetic parameter and operation the electromagnetic device until the first electromagnetic parameter substantially matches the known dry grain electromagnetic parameter.
In one implementation, the first electromagnetic parameter is the dielectric constant of the grain.
Other features and advantages will be readily apparent from the following description, the accompanying drawings and the claims.